High-order aberration correction for optimization of human visual function

ABSTRACT

The present invention relates to the optimization of human visual function by correcting and/or optimizing high-order optical aberrations in high performance optical devices. The optimization is particularly useful for high performance devices used under low light conditions such as binoculars, rifle scopes, telescopes, microscopes, night vision goggles and laser eye protection devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 11/749,721 filed 16May 2007, which claims benefit under 35 U.S.C. §119(e) from provisionalapplication Ser. No. 60/800,988 filed 16 May 2006, the contents of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the optimization of human visualfunction by correcting and/or optimizing high-order optical aberrations.The optimization is particularly useful for high performance activitiesespecially under low light conditions.

BACKGROUND OF THE INVENTION

The wavefront error of the human eye is analogous to the surface of adrum. The diameter of the drum represents the diameter of the pupil ofthe eye. If there were no aberrations, the surface of the drum would beflat. However, in almost any normal eye there are optical errorsrepresented by leads or lags in the wavefront, and in the analogy, hillsand valleys in the drum surface. Any smooth surface over a circularaperture can be described as a sum of coefficients multiplied by Zernikepolynomials. Optical aberrations in the human eye are now almostexclusively described in this manner. The lowest order Zernikeaberrations are shown in FIG. 1. Not shown in the “Zernike pyramid” arethe first two lines (radial orders) which include the Zernikes piston,tip and tilt. Conventional glasses include prism, sphere and cylindercorrection. Prism is simply tip and tilt, while sphere and cylinder arelinear combinations of defocus and astigmatism.

Shown in FIG. 1 are the 2^(nd) to 4^(th) order Zernikes.¹ Astigmatism,sphere, tip & tilt are considered “low-order” aberrations. All otheraberrations of higher radial order are known collectively as“high-order” aberrations. Conventional glasses attempt to provide thebest possible low-order correction.

Average pupil size significantly decreases with age. Persons of age 18yrs-40 yrs have pupil diameters in the neighborhood of 6.5 mm forlighting conditions typical of evening on an overcast day (44cd/m²).^(2,3) Average high-order root-mean-square (RMS) wavefront errorin a 6.5 mm pupil is of the order of 0.38 microns.⁴ Many people havegreater levels of high-order aberration. For comparison, to achieve asimilar RMS wavefront error in a 3 mm daytime pupil requires a1.2-diopter sphere error, which is considered large. Whereas residualsphere error can be nullified via the variable focusing power of thelens through the process of accommodation, the eye has no mechanism forchanging the amount of high-order aberrations.

Visual acuity characterizes the ability to resolve small objects. Acuitymeasures only a portion of visual ability. It is, however, one of themore well known measures of vision. Population averages of visual acuityversus age for normal healthy eyes are summarized in FIG. 2 which showsthe log MAR VA of 223 subjects ranging from 18 to 80 years of age. Thebest linear and bilinear fits to the data are shown.⁵ The subjects usedthe best possible conventional low-order correction for themeasurements.

In the graph of FIG. 2, 6/6 is the metric equivalent of 20/20. 6/3 isthe metric equivalent of 20/10 and represents approximately thepredicted Nyquist resolution limit due to the cone density in the humanfovea.⁶ Theoretically, if there were no optical aberrations, the humaneye should be capable of seeing approximately 20/10, although the exactvalue probably varies from person to person. Until recently, the world'srecord was 20/8. Young people of age 25-29 typically have the bestacuity, and vision generally worsens with increasing age after about age30. The reason for the decline with age is a topic of debate. The threemain theories include increases in high-order aberrations andconcomitant reduction in pupil size, increases in intraocular scatterand transmission loss, and loss of cones and/or ganglion cells.Published reports tend to support the first two theories for normalhealthy eyes.

The reason for the scatter in the data at any given age, especially forthe younger eyes, is probably mostly due to the presence of high-orderaberrations. One theory is that if a person was never exposed to goodvision when young, the neural development may preclude seeing at or nearthe Nyquist resolution limit later in life, a condition referred to asrefractive amblyopia.⁷ Nevertheless, when high-order aberrations arecorrected using adaptive optics, the visual acuity of all subjectssignificantly improves⁸. In a recent study, half of thehigh-order-corrected subjects consistently demonstrated an acuityexceeding 20/8.⁹ Therefore, vision benefit from correction of high-orderaberrations is not just theoretical.

One of the largest anticipated benefits of high-order aberrationcorrection is an improvement in contrast sensitivity. In low-lightconditions when the pupil diameter and the level of high-orderaberrations both increase, contrast sensitivity begins to degrade. Thishas two deleterious effects. One is that it may no longer be possible todetect certain low-contrast objects which are important in for exampledriving, hunting and military applications. The very definition ofcamouflage is to reduce contrast by better matching the surroundingconditions. The other problem is that even if an object can be detected,the detection and recognition process will take longer. Studiesconsistently show that reaction times are increased when contrastsensitivity is degraded.^(10,11)

The three major higher-order aberrations affecting typical peopleinclude coma, trefoil and spherical aberration. Coma is a non-symmetricaberration capable of causing significant loss of contrast sensitivity.FIG. 3 shows a high-contrast eye-chart optical simulation for a subjectwith 0.19 microns RMS of coma in a 6.0 mm pupil.¹² This is within astandard deviation of the average value.¹³ The simulation assumes thatall other aberrations are fully corrected. The top line is 20/100.

In a low contrast situation, the letters would be even more difficult torecognize, and of course, there are many other possible aberrationsbesides coma. For comparison, an un-aberrated (no aberrations) eye chartsimulation based on a 6.0 mm pupil is shown in FIG. 4.

The modulation transfer function (MTF) characterizes how well an opticalsystem preserves contrast versus spatial frequency. The MTF of adiffraction-limited eye having no aberrations with a 6.0 mm pupil isshown in FIG. 5.

The MTF graph with the introduction of just the 0.19 microns of coma ina 6.0 mm pupil is seen in FIG. 6.

The MTF curve is severely depressed at all spatial frequencies, due tothe single aberration of coma. If sphere and cylinder are not alsooptimally corrected, there will in addition be severe contrast lossesdue to low-order aberrations.

SUMMARY OF THE INVENTION

The present invention provides a personalized correction andoptimization of high-order aberrations of the human eye when usingbinoculars, rifle scopes, telescopes, microscopes, night vision gogglesand laser eye protection devices. The present invention willsignificantly enhance contrast sensitivity and low-contrast visualacuity in these devices. These vision benefits will be realized and willbe of significant use in enhancing both military and civilianperformances when using the above-identified devices.

TECHNICAL OBJECTIVES

Contrast sensitivity and low-contrast visual acuity is improved whenusing binoculars with the addition of personalized high-order aberrationcorrection and optimization.

Contrast sensitivity, low-contrast visual acuity and vernier acuity areimproved when using rifle scopes with the addition of personalizedhigh-order aberration correction and optimization. Marksmen are able tobetter group their shots when using high-order aberration correction andoptimization.

Contrast sensitivity is improved in night vision goggles by the additionof personalized high-order aberration correction and optimization, andwith MTF control to limit aliasing in the IIT.

Contrast sensitivity and low-contrast visual acuity is improved whenusing laser eye protection devices with the addition of personalizedhigh-order aberration correction and optimization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows graphic representations of 2^(nd) through 4^(th) orderZernike aberrations.

FIG. 2 is a graph showing population averages of visual acuity versusage for normal healthy eyes.

FIG. 3 is a high contrast eye chart optical simulation for a subjectwith 0.19 microns RMS of coma in a 6.0 mm pupil.

FIG. 4 is an optical simulation of an eye chart for a subject with a 6.0mm pupil with no aberrations.

FIG. 5 is a graph showing the MTF of a subject with a 6.0 mm pupil withno aberrations.

FIG. 6 is a graph showing the MTF of a subject with a 6.0 mm pupil with0.19 microns of coma.

FIG. 7-FIG. 11 show various PSF and MTF graphs made with Visual OpticsLab VOL-CT software, version 6.89.

FIG. 12 is a total aberration fringe pattern (OD).

FIG. 13 is a graph showing binocular efficiency versus magnification.

FIG. 14 is a graph showing the longitudinal chromatic aberration of thehuman eye.

FIG. 15 is a diagram showing the operation of a diffractive wave frontsensor that employs the self-imaging Talbot effect.

FIG. 16-FIG. 18 show theoretical and actual fringe patterns based on aprogrammed high order lens.

DETAILED DESCRIPTION OF THE INVENTION

Currently, aggressive high-order aberration correction can only beimplemented over a restricted field-of-view. Therefore devices thatnaturally operate with a restricted field-of-view are ideal candidatesfor this type of optical correction. Another category where high-orderaberration optimization is expected to be of major benefit involves lowlight conditions where the pupil size is significantly increased.Optical aberrations generally increase dramatically with pupil diameterand can therefore have a larger impact on vision. Four modes ofhigh-order wavefront correction in devices are included in the presentinvention. They are the following:

-   Binoculars-   Rifle Scopes-   Night Vision Devices-   Laser Eye Protection Spectacles/Goggles

The first three naturally employ a restricted field-of-view. The lasttwo modes intrinsically involve reduced levels of light entering theeye, forcing increased pupil sizes in all conditions. The first twomodes are often employed in low light conditions where pupil size isincreased.

The high-order aberrations of a subject are measured using a wavefrontsensor such as the Z-View® wavefront aberrometer (Ophthonix, Inc. SanDiego). A high-order aberration correction element is then manufacturedemploying well known technology and incorporated into the device ofinterest as a removable element. This aberration correction element willin addition to correcting and optimizing high-order aberrations of theuser's eye, also correct residual high-order error in the device itself.See, for example, U.S. Pat. Nos. 6,813,082; 6,989,938; 6,682,195;6,712,466; 6,840,619; 6,942,339; 7,021,764; 6,781,681; 7,034,949;6,761,454; 6,836,371; 6,934,088 and 6,976,641, each of which is herebyincorporated herein by reference in its entirety.

Optimal High-Order Aberrations

Characterizing the quality of vision is a complicated task because thereare multiple independent aspects and numerous metrics of vision.However, two classes of metrics that are widely used are acuity andcontrast sensitivity. If the human eye is made diffraction limited(meaning that all aberrations are erased) for a large pupil diametersuch as 5 mm, both contrast sensitivity and acuity will be degraded tonon-optimal values compared to what is possible. To better understandwhy this is so, and to envision what is necessary for optimal vision,the situation from both viewpoints will be examined.

Contrast Sensitivity

Contrast sensitivity involves the detection of sinusoidal gratings. Inorder to correctly identify the direction and frequency of a gratingimaged onto a detector such as the retina, the Nyquist criterion is tohave a minimum of two detection elements (e.g. foveal cones) perwavelength. The spacing of the cones in the fovea is of the order of 2.5microns, corresponding to roughly 30 arc-seconds. This leads to an oftenquoted maximum resolution of about 60 cycles per degree (cpd)corresponding to 20/10 Snellen acuity.¹⁴

It is possible, using the interference of two laser beams, to producesinusoidal gratings of any desired wavelength on the retina, bypassingthe optics of the eye. When this is done, subjects correctly identifythe wavelength and orientation of gratings below 60 cpd. However, whenshorter wavelengths are produced on the retina, a pattern is still seenby the subject, but the wavelength and orientation reported areincorrect. When gratings above the Nyquist limit are caused to move,they are perceived to move in the wrong direction. What happens is thatthe optical power above 60 cpd is aliased to spatial frequencies below60 cpd, and therefore constitutes noise.¹⁵ Allowing spatial frequenciesabove the Nyquist limit to activate the retina is counterproductive andhinders correct recognition of a scene, although it still contributes toraw detection indicating that something is there. A distinction is madebetween detection acuity and resolution acuity. Detection acuity is theability to tell if something is there, or if something has changed. Itis resolution acuity that allows personnel to correctly recognize andidentify objects and determine their direction of motion. A pilot withgood detection acuity but poor resolution acuity might well be able tosee another plane in the air at great distance, but he would incorrectlyconclude that the plane was closer by and misjudge its direction ofmotion due to retinal aliasing to lower spatial frequencies. It isresolution acuity that should be maximized in order to optimize militaryfunction.

Exactly the same phenomenon occurs in digital cameras. If the optics ofthe camera lens is too good, aliasing causes degradation of the imagewhen photographing scenes containing high enough spatial frequencies.This is typically remedied with the use of anti-aliasing filters.

The modulation transfer function or MTF is a measure of the amount ofcontrast transferred from the object to the image by an optical system.It is typically specified as a function versus spatial frequency. It isa measure of the quality of the optics. Higher MTF is generally a goodthing, unless the spatial frequency is above the Nyquist limit for thedetecting element. From the standpoint of MTF, the optimum thing to dois to maximize MTF below Nyquist, and minimize it above Nyquist. Onceagain, for the human eye, Nyquist is roughly 60 cpd. MTF for adiffraction limited eye with pupil diameter ranging from 2 mm to 8 mm isplotted in FIGS. 7-11. Above 3 mm diameter, the MTF above 60 cpd beginsto rapidly increase. The point being that one doesn't want a diffractionlimited eye with a pupil diameter bigger than about 3 mm. Therefore, theaberration structure beyond the central 3 mm diameter should be such asto maximize MTF below Nyquist, while minimizing it above Nyquist. Thisis accomplished by having the correct amounts of symmetric high-orderaberrations.

Acuity

One may imagine that the situation for acuity is different. If one istrying to resolve a crisp edge on a high contrast object, how can betteroptics hurt? The point spread function or PSF is the distribution oflight on the retina when looking at a point source of light such as astar. The PSF diameter or full width at half maximum (FWHM) becomessmaller as the pupil size becomes larger if there are no opticalaberrations. Should it matter if the PSF becomes smaller than a singlecone photoreceptor?

The fallacy in this thinking originates from failing to appreciate howthe brain perceives location using the retinal information. It is wellknown that humans can routinely detect location to sub-foveal-coneaccuracy. In vernier-acuity tests, typically people can align threepoints to less than 2 arc-seconds. A foveal cone photoreceptor has adiameter equivalent to 35 arc-seconds. What happens is that the PSFoverlaps several cones simultaneously, and the brain interpolatesposition to sub-cone accuracy.¹⁶ Were the PSF to become so narrow thatonly a single cone is illuminated at a time, the possible accuracy woulddecrease to 35 arc-seconds or one cone diameter.

Vernier acuity is very important for vision. It allows the brain togauge distance very accurately by noting the slightly differentpositions of an image upon the retinas of the two eyes.

From the standpoint of acuity, the best thing to do is to make a PSFthat has a diameter encompassing several cone photoreceptors, preferablythree. A symmetrical PSF is better than an unsymmetrical one, sooptimally all azimuthally non-symmetric aberrations should be correctedand eliminated. The diameter of a cone photoreceptor is roughly 30arc-seconds or about a half arc-minute. The FWHM of the PSF for adiffraction-limited eye with pupil diameter ranging from 2 mm to 8 mm islisted in the data column next to the plots in FIGS. 7-11. The diameterof the PSF reduces as the diameter of the diffraction limited pupilincreases. It can be seen that the multi-cone overlap criterion beginsto fail for diffraction-limited pupils larger than about 3 mm diameter.

MTF & PSF Calculation Versus Pupil Diameter

The calculations displayed in FIGS. 7-11 were made using Visual OpticsLab VOL-CT software, version 6.89 (See ref. 17). They show that the MTFabove 60 cpd, which is approximately the Nyquist resolution limit of thehuman fovea, increases when the pupil diameter increases beyond 3 mmdiameter when no aberrations are present. Simultaneously, the PSFdiameter decreases so that it no longer overlaps several cones. Fovealcone diameter is approximately 0.5 arc minutes.

Examples of Eyes with Excellent Vision

A clinical trial subject's right eye (Subject A) was measured at 20/12acuity without glasses or contacts, which is close to as good as it getsfor a young person. Subject A was 46 years old at the time, making hisacuity all the more impressive. He claimed that he could hit a 1″ targetat 60 yards with a pellet gun using open sights, which he describes as“scary good.” His high-order RMS on a 4.5 mm pupil was 0.66 microns, hislow-order RMS was 0.98 microns, for a total of 1.2 microns, which didnot sound very impressive. Even more puzzling at the time, it suggestedthat good acuity could come from an eye with significant amounts ofaberration. When a fringe pattern was plotted of his total eye, however,it showed that the center 3 mm diameter of his wavefront wasexceptionally flat, and at a larger radius the aberrations kicked inwith a vengeance. See FIG. 12. This illustrates that the rule-of-thumbto correct only the center 3 mm for best vision actually works. In hiscase, high-order astigmatism and spherical aberration are compensated bysphere and astigmatism in the central 3 mm zone.

Subject “B” had 0.03 microns RMS of high order aberration in each of hiseyes at 3.0 mm diameter, which is extraordinarily low. He could almostace the entire low contrast sensitivity chart. Some of the testspatterns could not be seen by many people when it was placed directly infront of their face. The answer key had to be consulted to see whetherhe was giving the correct answers. Wavefront data on his eyes could onlybe obtained out to about 3.0 mm because he had small pupils. His eyesillustrate that superb contrast sensitivity is possible with perfect 3mm pupils. Larger pupils are not required for extraordinary contrastsensitivity.

In a recent experiment using adaptive optics, the vision of threesubjects was fully corrected over a 3 mm diameter pupil, and then over a5.8 mm diameter pupil.¹⁸ The Nyquist resolution limit for the humanfovea is predicted to be about 20/10 and the world record previouslymeasured was 20/8. Acuity with the 3 mm correction was measured at 20/7in all three subjects, essentially matching the world record. However,vision did not further improve with the 5.8 mm correction. The detailsprovided in the abstract did not indicate whether visual performanceactually degraded with the 5.8 mm correction. These results confirm thepredictions of the Nyquist resolution limit and are consistent with theidea that MTF above the resolution limit is not useful for resolutionacuity.

The optimal optical correction for the human eye is not to simplycorrect every aberration for a large pupil diameter. This is difficultfor many people to grasp initially. They have trouble believing thatbetter optics can sometimes degrade vision. The explanation lies in thestructure of the retina, not the optics.

To optimize vision for pupil diameters of 3 mm diameter or less, theoptimum thing to do is eliminate all aberrations. Perhaps surprisingly,for pupil diameters larger than 3 mm diameter the situation isdifferent. For pupils larger than 3 mm diameter, the optimum thing to dois to maximize MTF below Nyquist, and minimize it above Nyquist.Alternatively, the PSF should be made symmetrical and of such a diameterthat it overlaps approximately 3 photoreceptor cones in the fovea.

Implementation of High-Order Correction

Implementation of high-order correction in a practical manner iscurrently under development. Attempts to correct high-order usinginvasive procedures such as corneal surgery, and intraocular implantshave been stymied by uncertainties and variations in the aberrationsgenerated by the surgical and healing processes.¹⁹ Corneal laser surgeryhas a long history of making high-order aberrations levels considerablyworse. Using a wavefront aberrometer it is easy to identify a LASIK orRK subject, because their high-order levels are considerably elevatedabove the norm. A few subjects get lucky, but the majority suffers fromreduced contrast sensitivity due to the increase in high-orderaberrations caused by the surgery. The recent introduction of wavefrontbased correction techniques has brought the hope that perhapslaser/cornea surgery can avoid making the high-order levels worse onaverage. Contacts are another possibility, but a major issue involvesstabilizing the position and rotation of the contact in the optimumposition. The contact itself changes the aberrations of the eye and thishas to be reliably predicted and taken into account. High-ordercorrection with contacts has yet to be demonstrated. Clinical trialshave demonstrated improved visual performance with high order correctionin spectacle lenses.²⁰

Before high-order aberrations can be corrected and optimized, low-orderaberrations must be corrected. Due to difficulties in accuratelyrefracting subjects, the optimum low-order prescription is not alwaysobtained. The Z-View® wavefront aberrometer (commercially available fromOphthonix, Inc., San Diego) quickly and accurately refracts the humaneye, and determines the optimum low-order prescription. It accomplishesthis without the subjective input of the subject, and reduces the chanceof human error. In addition, it provides a complete analysis ofhigh-order aberrations. Wavefront guided lens technology then allows forthe correction of high-order aberrations in spectacles and otherdevices. See for example U.S. Pat. Nos. 6,813,082; 6,989,938; 6,712,466;6,840,619; 6,942,339; 7,021,764; and US Patent Publication 2006/0052547all of which are incorporated herein by reference.

Adaptation

Vision involves three main factors; the optics of the eye, the retinaand the brain. The optics determines the MTF and PSF. The retinalstructure imposes constraints on the PSF and MTF, which the optics mustprovide for optimum vision. Finally, what a person actually sees issomething computed by the brain, based upon the information from theeye. Due to aberrations in the eye, images of straight lines on theretina are in fact distorted and blurry. However, we nevertheless seestraight lines and we do not notice the blurriness.²¹ This is due toprocessing in the brain.

In a fascinating experiment involving adaptive optics, subjects hadtheir aberrations erased and then recreated in a rotated form.²² What isinteresting is that the subjects suffered from significantly decreasedacuity and contrast with the rotated aberrations. After a half-hour ofviewing with the new optical situation, a large portion of the visionloss disappeared. The conclusion is that the brain adapts to theaberrations present in the eye, and this adaptation improves visualability. However, it takes time to adapt to a new aberrationconfiguration. It is not known how long of an adaptation period isrequired for maximum benefit to be realized. However, in many situationsthree days has been shown to be sufficient. For instance when gogglesare worn that flip the images of the world upside down, three days laterthe person is able to function in a completely normal fashion, signingchecks and shaking hands etc.²³ When the goggles are then removed,normal function is retained because the brain still has the previouslyused software, however there is an eerie sensation for an hour or so. Asmall scotoma generated by laser damage will continue to obscure aportion of the visual field, but will not be continuously noticeable bythe subject several days later. These and other examples suggest thatseveral days are sufficient to allow for significant levels ofadaptation.

The result is that when high-order aberration correction is implemented,personnel should not expect to experience the maximum visual benefitinstantaneously. Rather a few days of adaptation should be allowed toallow the brain to learn to use the new situation in the optimalfashion.

Application of High Order Correction to Military and Sporting DevicesBinoculars

Binoculars represent a highly evolved optical device with a long historyof development.²⁴ In essence binoculars are two telescopes set side byside to allow for binocular viewing of a magnified image.²⁵ Since abinocular extends the range of human vision, one figure of merit forbinocular performance is the maximum range at which a target can bedetected using the binocular. Binocular efficiency is defined²⁶ as

$E = \frac{R}{r}$

where E is the binocular efficiency, R is the range at which the targetis detected with the binocular, and r is the range at which the targetis detected with the unaided eye. Experiments show that the binocularefficiency decreases from ideal values as magnification is increased²⁷,more so for hand held binoculars as shown in FIG. 13.

For the hand-held case, simple models indicate that the drop off withincreasing magnification is mostly due to tremble or shake induced bythe user. A smaller portion of the efficiency loss is due to opticalimperfections in the optics of the binoculars which increases with lenspower and magnification. The probability of recognizing equal-sizedimages of objects in a given time is reduced, and the recognition timeincreases approximately proportionally to the increase inmagnification.²⁸ Observation time is not unlimited. Experience with alarge number of individuals using binoculars with 10× to 15×magnification for a prolonged period of time using complete focusedattention has shown that the maximum possible observation period amountsto 2-3 min on the average.²⁹ Research has also demonstrated thatlow-contrast detection tasks are far more sensitive measures ofbinocular performance than high-contrast bar charts.³⁰

The equation defining binocular efficiency can be recast as:R=E·r

In order to increase the range R at which an object could be detected,one can either increase the binocular efficiency E, the range r at whichthe object can be detected without the binoculars, or both. Bycorrecting aberrations in the binocular optics, small improvements in Emay be possible. By correcting aberrations in the eyes of the user,significant improvements in r should be possible, especially in lowlight conditions where the pupil diameter is increased. Both correctionscan be done simultaneously in a single aberration correcting opticalelement.

Ideally the high-order aberration correcting element based onaberrations measured at the position of the cornea would be positionedat a location in the optical system conjugate to the cornea. The lightexiting the eyepiece of a telescope or binocular is approximatelycollimated, and therefore the phase plate could be made to fastenexternally onto the eyepiece. Corrections due to the finite distancefrom the cornea can be calculated and incorporated into the design.However, these corrections are likely to be small. High-order correctionhas been shown to be relatively insensitive to axial position (distancefrom the eye). In a study involving phase plate correction of threehuman subjects, two of the three subjects maintained 95% correction whenthe phase plate was moved 5 pupil radii away from the optimumposition.³¹ The third and worst case had the degree of compensationreduced to 85%, which is nevertheless a very respectable correctionlevel. What this means is that high-order correction in optical deviceslike telescopes and binoculars is easy to test, because it is notnecessary to “hack” into the optical device, one simply needs to affix aphase plate to the eyepiece. It also means that although the opticalcorrection is personalized, the optical device itself is not. It can beused by any personnel. Anyone who has a personalized corrector platemanufactured for their eye can use the device in an enhanced mode withsuper normal vision capability. Testing of the concept isstraightforward. Placebo phase plates with no correction and high-ordercorrecting phase plates are affixed to the eyepieces in a double-maskedstudy and the vision testing results compared.

Rifle Scopes

A typical task in a rifle scope is to line up a reticule with an objectin the background. Optimization of this task requires optimization ofvernier acuity. In its simplest form, vernier acuity involves thejudgment of when two lines are aligned. Foveal cones in the human eyeare separated by roughly 35 arc seconds, so that one might naivelyassume that the best possible alignment is to within about 35arc-seconds. However, humans can routinely align such lines to betterthan 2 arc seconds.³² This is possible only because the width of imageof the line on the retina is wide enough to encompass several cones, andthe brain learns to interpolate position to sub-cone-spacing accuracy.

High-order aberrations can distort the shape of the line on the retina,lower contrast to make the line more difficult to detect, andexcessively broaden the width of the line, leading to reduced vernieracuity. However, if one were to correct all optical aberrations over saya 5 mm diameter pupil typical in dim lighting, the width of the image ofa narrow line on the retina would be less than the width of a singlecone. In this case, vernier acuity would actually deteriorate to 35 arcseconds, because interpolation would be impossible. This exampleillustrates that naively correcting all high-order aberrations over alarge pupil (larger than 3 mm diameter) is actually counter productive.It also demonstrates that there are two completely different ways tosuffer reduced vernier acuity, too many high-order aberrations in asmall pupil, or too few aberrations or more correctly a non-optimalhigh-order aberration structure in a large pupil. For this reason, it isperhaps more appropriate to refer to high-order aberration“optimization,” rather than simply “correction.”

The ultimate test is to have a double masked study using experiencedmarksmen, using either plano optical elements containing no correctionor with personalized high-order corrector elements attached to theirscopes. The study would look for statistically significant tightergrouping of the bullet holes in the targets with the use of high-ordercorrection. Before this test, however, simple increases in contrastsensitivity and acuity with the use of high-order correction will belooked for.

Night Vision Devices

Military, police and sporting activities frequently take place in lowlight conditions such as at night and the use of night vision devices(NVDs) and night vision goggles (NVGs) in particular is now commonplace.The resolution of NVGs is primarily limited by the image intensifiertube (IIT), is of the order of 30 line pairs per millimeter out of theIIT, and results in a visual acuity limitation of approximately 20/40.There are two separate areas where a programmable wavefront optic mightimprove visual function with an NVG:

-   -   Minimizing alias noise generated at the photocathode by        controlling MTF on the objective side    -   Optimizing the high-order aberrations of the user who typically        has dilated pupils due to the lower light levels, and        controlling MTF on the eyepiece side

Objective Side—The image intensifier tube (IIT) has a limitingresolution at something like 30 line pairs per mm. Any component of thelight transmitted by the objective that has spatial frequency content inexcess of the spatial frequency limit will be detected by the imageintensifier tube but will be aliased to a lower spatial frequency andend up as noise. Ideally the modulation transfer function or MTF for theobjective would be as large as possible below the spatial frequencylimit, but as small as possible above the limit. However, in order to bevery successful at this, the optical designer would need access to avariable amount of very specific azimuthally symmetric aberration thatcould be introduced to the objective. Other issues often dominate theselection of the lenses used, which invariably are commercial off theshelf optics. However, using wavefront programmable lens technologydescribed herein, the optimal high-order aberration could be easilymanufactured. This corrector plate will improve contrast sensitivity byminimizing a major source of noise.

Eyepiece Side—Because the image intensifier tube is limited in spatialresolution, any MTF in the eyepiece optics above the spatial frequencylimit can only deliver noise to the eye. MTF above the spatial frequencylimit can be minimized by controlling the azimuthally symmetricaberrations of the eyepiece optics. A corrector plate for the eyepieceside can be made which controls the MTF in the desired fashion. Thecorrector plate can also optimize the high-order aberrations specific tothe user's eye. The aberrations of the user would be measured using awavefront aberrometer. The pupil diameter can be estimated from thescene luminance presented to the eye. This is typically 2-4.5 cd/m²resulting in an average pupil diameter larger than 5 mm for youngadults.³³ Even with the image intensifier, light levels presented to theeye are far below daytime levels, and the pupil diameter issignificantly increased. Levels of high-order aberrations dramaticallyincrease with pupil diameter, and affect contrast sensitivity. Withoptimization of the user's high-order aberrations, contrast sensitivitywill be optimized.

With the above enhancements there may be a slight increase in acuitythrough the system, but due to the limitation of the IIT this may besmall. However, acuity is but one measure of vision, and it does notfully describe visual function. Contrast sensitivity is a better measureof visual function. Two personnel with identical acuity can have verydifferent contrast sensitivity curves. The person with better contrastsensitivity will see better, and recognize and react faster. Acuity is ameasure of the contrast sensitivity only at the highest detectablespatial frequency. The significant contrast improvement and noisereduction anticipated with high-order correction of NVGs should resultin better visual function, and faster recognition and reaction times.NVGs can be tested in a double masked study both with and without theoptimum personalized correction optics. Placebo correction plates withno optical power would be used for the null case.

Laser Eye Protection Spectacles/Goggles

With evolving technology, lasers very dangerous to the human eye havebecome more affordable and widespread. Mass produced lasers packaged inthe form of laser pointers are approaching the class-IV laser safetydesignation (>0.5 watt average power), meaning that they can fairlyeasily start fires.³⁴ The result is that the use of lasers that are noteye safe is almost certain in modern warfare. And it is not just theenemy that US personnel must be concerned with. The US military itselfutilizes numerous dangerous lasers, and numerous accidents have beendocumented.³⁵ Recently commercial airline pilots have reported laserbeams aimed at in-flight commercial airlines. The result is that alldeployed personnel may occasionally be required to wear laser eyeprotection (LEP) goggles or spectacles. A disadvantage of LEP is that inorder to protect against most major threat wavelengths, a substantialproportion of the available light must be blocked. The laser eyeprotection devices therefore often resemble dark sunglasses. In lowlight conditions such LEP devices severely degrade vision. Anyenhancement to vision that can be obtained while wearing LEP devices isthus in great demand.

In reduced lighting the pupil diameter increases and high-orderaberrations levels dramatically increase. This is precisely thecondition where high-order aberration optimization and correction willprovide the maximum possible benefit. In addition to high-ordermonochromatic aberrations, there are also severe chromatic aberrationsin the human eye. Simultaneous correction of high-order aberrations andchromatic aberrations will have a synergistic effect, because these twocategories of aberrations compensate each other to a degree. Therefore,if chromatic aberrations are corrected in addition to monochromatichigh-order aberrations, the visual improvement will roughly double.³⁶

Chromatic aberration correction in the case of LEP would come fromspectral narrowing due to the filtering. The pass band of LEP devices isan evolving entity as laser technology itself evolves. However, somegeneral principles can be leveraged. Lasers generating near-infrared andred wavelengths are more economical per watt, and generally more compactand lightweight than shorter wavelength lasers, so consequently LEPdevices tend to block the near-IR and red end of the spectrum. The peakphotopic sensitivity is in the green, so the broadest protection whilepassing maximum luminosity is perhaps to block both the red and blueends of the spectrum. However, the availability of frequency doubledlasers operating at 532 nm may require blocking at that specific greenwavelength as well. The net effect of LEP filtering is to generallynarrow the spectral range entering the human eye. This reduces theamount of light entering the eye which generally reduces visual ability,and that is the problem. However, it also effectively reduces chromaticaberration, which if combined with high-order aberration correction willlead to improved visual function, and this is the opportunity.

The longitudinal chromatic aberration of the human eye³⁷ is shown inFIG. 14.

Between deep blue and deep red there is a 2.5 diopter difference, whichis enormous. What this means is that if one is focused perfectly fordeep blue, the deep red is 2.5 diopters out of focus. Several factorsmitigate the severity of this aberration. Primarily the photopicresponse curve shows that the eye is much more sensitive to green lightthan blue or red. Also, monochromatic high-order aberrations increasethe depth of focus of the eye and thereby combat chromatic aberration aswell.³⁸ Correction of chromatic aberration by itself through spectralnarrowing does not enhance acuity or contrast to a large degree,probably due to the interaction with monochromatic aberrations. Butcorrection of both chromatic and monochromatic aberrations will lead toa dramatic improvement in contrast and improvement in acuity.³⁹ Thespectral narrowing inherent in laser eye protection creates an idealsituation for high-order aberration correction to make a substantialimprovement in visual ability.

Generic LEP devices resembling spectacles or goggles differ from theother applications described herein in that the devices are notintrinsically limiting to the field of view. Spectacles are generallydesigned to minimally restrict the field of view. Therefore, since anaggressive high-order correction zone would itself have a limited fieldof view, the high-order zone would represent a vision “sweet spot” inthe LEP device. The situation is analogous to that of progressiveaddition lenses (PALs) worn by subjects over the age of approximately 45to combat presbyopia, or the inability to focus nearby. The near zoneand the addition channel in particular have a restricted field of view.Head motion is required to align the near zone or the addition channelwith the object of interest and this requires a few days of adaptation.Yet virtually all subjects can adapt to PALs, and PALs represent morethan half of all dispensed multi-focal lenses proving that a solutionwith a restricted field of view is acceptable.⁴⁰ What happens in thecase of PALs is that the brain learns to disregard the transition zonesaround the power channel and one only notices the beneficial powerincrease. The eyes and head learn to move so as to reap optimum benefitfrom the power channel.

In the case of high-order correction, the corrected field-of-viewdepends upon the spatial frequency content of the correction, and islarger for lower spatial frequency content. High-order correction can beimplemented so as to increase the field-of-view at the cost of some ofthe correction.⁴¹ Coma is the high-order aberration containing thelowest spatial frequency content. As such, it is the high-orderaberration that is easiest to correct while maintaining the largestpossible field-of-view. There are tradeoffs to be made betweenfield-of-view and degree of high-order optimization and correction.

In summary, LEP typically reduces chromatic aberration due to spectralfiltering. In such cases the vision benefit due to correction andoptimization of high-order aberrations will roughly double. In aspectacle or goggle format, aggressive high-order aberration correctionwill create a vision sweet spot that the user would have to adapt to andlearn to use.

The addition of high-order aberration correction significantly improvescontrast sensitivity and acuity after a suitable adaptation period.

Wavefront Aberrometer

Refracting subjects is time consuming, sometimes difficult and ofteninaccurate. A preferred wavefront sensor used in the practice of thepresent invention is a self-imaging diffractive aberrometer such as forexample the Z-View® aberrometer that can quickly and accurately refractsubjects, literally in the blink of an eye. Wavefront aberrationsincluding high-order aberrations are automatically recorded. Thisfingerprint of the eye contains complete information concerning theoptical quality of the eye. The novel design of the Z-View® aberrometergives it just as much accuracy but higher spatial resolution thanaberrometers based upon Hartmann-Shack sensors which are alsocommercially available and can also be used in taking wavefrontmeasurements according to the present invention.

FIG. 15 is a flow diagram showing the functions of a self-imagingdiffractive aberrometer which is based on a principle of wave opticscalled “self-imaging” or the Talbot Effect.⁴³ The Talbot Effect is basedon the fact that when certain intensity modulation patterns are placedat the optical pupil of a system and illuminated with plane waves,images reappear at predicable positions along the propagation path(Talbot Planes). Additional optical elements are not required to formthese images. A subset of the modulation patterns that self-imageinclude all periodic structures such as two-dimensional sinusoidalgratings. The modulation pattern can be recorded by an imaging detectorplaced at the position of one of the Talbot Planes. If the opticalsystem contains wavefront aberrations, the image of the modulationpattern will be distorted relative to the periodic modulation element.The distortions on the periodic “carrier” intensity pattern can beextracted through computer algorithms applied to the recorded intensityvalues. The computer algorithms are based on Fourier transformation ofthe measured intensity, and subsequent extraction of the aberrationinformation from the carrier signal. The diffractive sensor is describedin more detail elsewhere.⁴⁴

A typical Hartmann-Shack system utilizes 50-200 measurement pointswithin a 7 mm diameter pupil, and even the latest “high resolution”systems use approximately 3,500 points.⁴⁵ If the curvature of thewavefront varies significantly over a sub-aperture, either because theaberrations are of high spatial frequency, or because the aberrationsare of low spatial frequency but large in magnitude, the result is thatthe focused spots in an HS sensor become blurry and more difficult tolocate.⁴⁶ The self-imaging diffractive WFS utilizes a two-dimensionalgrating and has more than 17,000 effective elements over a 7 mm pupil.This higher spatial resolution makes it less likely to fail due to largewavefront curvature. However, both types of sensors experiencedifficulties if the spots or effective element images are displaced suchthat they overlap on the position sensitive detector. Due to the shortdistance between the grating and camera, 100 diopters of local powerbetween elements is required to cause element overlap in theself-imaging diffractive sensor.

Photopolymer Spectacle Technology

Conventional spectacles offer cylinder, sphere and prism compensationfor the eye's aberrations. iZon® spectacle lens technology includes aprogrammable optical layer, i.e., photopolymer layer, in which bothhigh-order and low-order aberrations can be corrected, and in whichdiffractive elements can be “written” on demand.⁴⁷ The index ofrefraction can be varied in the photopolymer layer to produce a variableindex of refraction profile that compensates for high order aberrationsof the eye or inherent aberrations in the lens. Aberrations caneliminated or modified to produce the optimal visual content. Basicallyany imaginable optical design can be programmed in the lens to a veryprecise level. The principal high-order aberrations are coma, trefoiland spherical aberration. Coma, which is an aberration producing acomet-like tail on the point spread function or PSF, significantlyreduces contrast sensitivity. Spherical aberration can directly affectthe minimum retinal spot size and thus acuity. Therefore, high-orderaberration optimization and correction can have very significant impacton vision. Using diffractive designs programmed into a photopolymerlens, prism could be produced in a thinner, lighter spectacle.Diffractive elements can also remove chromatic aberration due toconventional prisms and large prescriptions, and markedly increase thedepth of focus.⁴⁸ By programming optical patterns tailored to theindividual subject, a subject's retinal image can be warped arounddysfunctional retinal tissue, thereby eliminating a substantial blindspot.⁴⁹ By combining free-form surface generators with the programmablephotopolymer layer, virtually any imaginable optical element can becreated.

iZon® photopolymer lenses are comprised of three layers. The outerlayers are composed of a high-index ophthalmic polymer. The centrallayer is a thin programmable polymeric layer in which the index ofrefraction can be altered.⁵⁰ This refractive index alteration isprogrammable with the application of ultraviolet light, and virtuallyany conceivable pattern can be generated. There are dynamic rangelimitations, and typically the gradient index pattern written into thepolymeric layer is combined with surface profile generation on one ormore of the outer layers to produce the desired optical design. Thegradient index layer can be fixed to make it immune to further UVexposure. The spectacle lenses may then be exposed to direct sunlightwithout degradation of the optical profile.

Laser-based direct digital lens writers are employed to program adesired pattern into the polymeric layer. Either bitmaps or Zernikevalues can be used to specify a written pattern. FIGS. 16 and 17demonstrate specific Zernike patterns 6 mm in diameter, programmed intophotopolymer lenses. FIG. 16 shows the theoretical and actual fringeswritten in a photopolymer lens; 0.20 μm Z_(4,−4)+0.29 μm Z_(4,0) whileFIG. 17 shows theoretical and actual fringes written in a photopoymerlens; 0.21 μm Z_(4,−2)+0.29 μm Z_(4,0)

Theoretical fringe patterns are shown as well as the actual fringepattern recorded using a Zygo interferometer. In FIG. 18, the2^(nd)-order aberrations in a lens blank have first been erased in acircle 8 mm in diameter, illustrating that aberrations introduced duringconventional manufacturing processes can be corrected. Then a correctionfor the eye aberrations of a subject have been written in the zone,illustrating that high-order aberration correction is achieved with thistechnology. Comparison with the theoretical fringe pattern showsexcellent agreement.

Public Purpose

The present invention is directed toward improving human vision whenusing specific devices frequently used in the military. However, many ofthe same or similar devices are used by the general public. Hunters userifle scopes and would benefit from enhanced vision in the morning orevening when light levels are low. Persons with low vision often usesmall telescopes to see distant objects such as road signs. Since mostof these persons use eccentric viewing, their levels of high-order comaare significantly elevated, and they may benefit greatly from high-orderaberration correction and optimization. Many people use binoculars invarious situations, including bird watchers, rangers, hunters andwildlife enthusiasts, and many would benefit from improved vision whenusing the devices. The technology described here is applicable tomicroscopes and telescopes. For instance, astronomers and pathologistsmay prefer to have personalized eyepieces that allow them to see moreclearly through their devices. With decreased recognition timesassociated with improved levels of contrast sensitivity, productivitymay be expected to increase. With increases in acuity, more informationwill become available when using the devices. If the LEP applicationwith its chromatic correction indeed produces a doubled vision benefit,an entirely new avenue of specialized vision optimization will be openedup. Spectral narrowing sunglasses with a super-normal-vision sweet spotwill find use by many in the general public, as well as by people inother governmental agencies.

Exemplary Methods

Binoculars

30 subjects are recruited for a clinical trial. The high-orderaberrations of study subjects are measured using the Z-View® wavefrontaberrometer. The aberrations of the binoculars to be used in the study(typical military binoculars) are measured using an interferometer.High-order aberration correcting optical elements based upon thecombined subject measurements and device measurements are made to beaffixed to the eyepieces of the binoculars. If the device (binocular)optical errors are potentially significant, then high-order correctingoptical elements based only upon the subject device measurements aremade so as to later be able to estimate the contribution due to deviceoptical errors. A placebo optical correcting element containing nohigh-order aberration correction is also made so neither test subjectsnor medical personnel know which correcting elements are being usedduring the test. Using a double masked clinical trial, contrastsensitivity and low-contrast visual acuity using the binoculars under arange of documented lighting conditions with minimal time for adaptationare measured. Subjects completing the clinical trial will next berequired to spend a minimum time of 8 hours accumulated over the nextseveral weeks looking through the binoculars with high order aberrationcorrection to provide time for adaptation. Accumulated time lookingthrough the binoculars will be estimated and recorded. The double maskedclinical trial is repeated (including placebo) measuring contrastsensitivity and low-contrast visual acuity using the binoculars under arange of documented lighting conditions. Binoculars providing high ordercorrection will provide better vision.

Rifle Scopes

30 subjects are recruited for a clinical trial. These will be subjectsthat are at least minimally experienced at shooting a rifle using ascope. The high-order aberrations of study subjects are measured usingthe Z-View® wavefront aberrometer. The aberrations of the rifle scopesto be used in the study are measured using an interferometer. High-orderaberration correcting optical elements based upon the combined subjectmeasurements and device measurements are made to be affixed to theeyepiece end of the rifle scope. If the device (rifle scope) opticalerrors are potentially significant then high-order correcting opticalelements based only upon the subject measurements are made so as tolater be able to estimate the contribution due to device optical errors.A placebo optical correcting element containing no high-order aberrationcorrection is also made so neither test subjects nor medical personnelknow which correcting elements are being used during the test. Using adouble masked clinical trial, contrast sensitivity, low-contrast visualacuity and vernier acuity using the rifle scopes under a range ofdocumented lighting conditions with minimal time for adaptation aremeasured. Subjects completing the clinical trial will next be requiredto spend a minimum time of 8 hours accumulated over the next severalweeks looking through the rifle scope with aberration correction toprovide time for adaptation. Accumulated time looking through the scopewill be recorded. The double masked clinical trial is repeated(including placebo) measuring contrast sensitivity, low-contrast visualacuity and vernier acuity using the rifle scopes under a range ofdocumented lighting conditions. A clinical trial at a shooting range isthen is then conducted with test subjects in the study group. Subjectsusing the rifle scopes with high order correction attachments will havebetter shooting scores.

Night Vision Goggles (NVGs)

30 subjects are recruited for a clinical trial. The high-orderaberrations of study subjects are measured using the Z-View® wavefrontaberrometer. The aberrations of the eyepieces and objective optics ofthe NVGs to be used in the study (a typical military NVG) are measuredusing an interferometer. High-order aberration optimizing opticalelements based upon the combined subject measurements and devicemeasurements for the eyepiece are made to be affixed to the eyepiece ofthe NVGS. High-order aberration optimizing optical elements based uponthe device measurements for the objective end are also made to beaffixed to the objective end of the NVGs. If the device optical errorson the eyepiece end or objective end are potentially significant,high-order correcting optical elements based only upon the subjectmeasurements are also made so as to later be able to estimate thecontribution due to device optical errors. A placebo optical correctingelement containing no high-order aberration correction is also made forboth ends so neither test subjects nor medical personnel know whichcorrecting elements are being used during the test. Using a doublemasked clinical trial contrast sensitivity and low-contrast visualacuity using the NVGs under a range of documented lighting conditionswith minimal time for adaptation are measured. Subjects completing theclinical trial will next be required to spend a minimum time of 8 hoursaccumulated over the next several weeks looking through the NVGs withaberration correction to provide time for adaptation. Accumulated timelooking through the NVG will be estimated and recorded. The doublemasked clinical trial is repeated (including placebo) measuring contrastsensitivity and low-contrast visual acuity using the NVGs under a rangeof documented lighting conditions. NVGs containing high order aberrationcorrection will provide better vision.

Laser Eye Protection (LEP)

30 subjects are recruited for a clinical trial. The high-orderaberrations of study subjects are measured using the Z-View® wavefrontaberrometer. An LEP device is selected to be used in the study whichalso has significant spectral narrowing. Spectral narrowing is measuredusing spectrometers and densitometers. A photopolymer programmableoptical element is made having the same spectral transmission. There aretwo parallel approaches to be pursued. One is to manufactureprogrammable lenses using lens blanks obtained from the LEP manufactureror to modify the actual finished LEP devices themselves. The simplestmethod is to obtain the raw dyed and/or coated lens blanks from the LEPmanufacturer and apply a photopolymer coating having the high ordercorrection programmed in the photopolymer layer. The photopolymer layeris then hard coated preferably using a vacuum coating facility.Alternatively, the actual LEP device is converted to a programmable lensthrough a thinning and lamination process. The other approach will be tomimic with sufficient accuracy the optical density versus wavelengthproperty of the LEP in a photopolymer lens using dyes and coatings.Examples of dyes that are available include A-195 from GentexCorporation and others available from Glendale Laser Eyewear andSpecialty Filters. High-order aberration correcting optical elementsbased upon the combined subject measurements and device measurements aremade. A placebo optical correcting element containing no high-orderaberration correction is also made so neither test subjects nor medicalpersonnel know which correcting elements are being used during the test.Using a double masked clinical trial, contrast sensitivity andlow-contrast visual acuity using the LEP devices under a range ofdocumented lighting conditions with minimal time for adaptation aremeasured. Subjects completing the clinical trial will next be requiredto spend a minimum time of 8 hours accumulated over the next severalweeks looking through the LEP devices with high order aberrationcorrection to provide time for adaptation. Accumulated time lookingthrough the LEP devices will be estimated and recorded. The doublemasked clinical trial is repeated (including placebo) measuring contrastsensitivity and low-contrast visual acuity using the LEP devices under arange of documented lighting conditions. A questionnaire is filled outby the study participants concerning their impression of the usefulnessof the vision “sweet spot” and their adaptation experience while usingthe vision sweet spot in the LEP device. The LEP devices providing highorder aberration correction provide better vision.

REFERENCES CITED

-   (1) Raymond Applegate, “Zernike Expansion,” Wavefront Congress    presentation, http://129.7.217.162/presentations.htm; David    Atchison, “Recent advances in the representation of monochromatic    aberrations of human eyes,” Clin Exp Optom, Vol. 87, No. 3 (2004)    pp. 138-148-   (2) Barry Winn, David Whitaker, David B. Elliot, Nicholas J.    Phillips, “Factors affecting light-adapted pupil size in normal    human subjects,” Invest. Ophthalmol. & Visual Sci, Vol 35, No. 3,    (1994), pp. 1132-37-   (3) RCA Electro-Optics Handbook, 2nd edition (1974 RCA    Corporation), p. 70-   (4) L. Thibos, X. Hong, L. Bradley, X. Cheng, “Statistical variation    of aberration structure and image quality in a normal population of    healthy eyes,” J. Opt Soc Am A, Vol. 19, No. 12 (2002) pp. 2329-2348    (FIG. 9)-   (5) David Eliot, Kathy Yang, David Whitaker, “Visual Acuity Changes    Throughout Adulthood in Normal, Healthy Eyes: Seeing Beyond 6/6,”    Opt Vis Sci Vol. 72, No. 3, (1995) pp. 186-191-   (6) R. Applegate, “Limits to Vision: Can we do better than    nature?” J. Refract Sur, Vol. 16, (September/October 2000) pp.    S547-S551-   (7) IBID, Applegate (2000) p. 5548-   (8) S. Poonja, S. Patel, L. Henry, A. Roorda, “Dynamic visual    stimulus presentation in an adaptive optics scanning laser    ophthalmoscope,” J. Ref. Sur., Vol 21, (September/October 2005) pp.    S575-S580-   (9) E. A. Rossi, A. Roorda, “The limits of high contrast photopic    visual acuity with adaptive optics,” Poster 5402, ARVO, May 4, 2006,    abstract available at www.iovs.org-   (10) W. G. Bachman, T. A. Winegert, C. j. Bassi, “Driver contrast    sensitivity and reaction times as measured through a salt-covered    windshield,” Optometry Vol. 77 (2006) pp 67-70-   (11) C. F. Stromeyer, P. Martin, “Human temporal impulse response    speeds up with increased stimulus contrast,” Vis Research, Vol. 43,    No. 3 (2003) pp. 285-98-   (12) Simulations made using commercially available software,    “VOL-CT,” Sarver and Associates, www.sarverassociates.com-   (13) L. Thibos, X. Hong, L. Bradley, X. Cheng, “Statistical    variation of aberration structure and image quality in a normal    population of healthy eyes,” J. Opt Soc Am A, Vol. 19, No. 12 (2002)    pp. 2329-2348-   (14) The prospects for super-acuity: limits to visual performance    after correction of monochromatic ocular aberrations, W. N. Charman    and N. Chateau, Ophthalmology and Physiological Optics, Vol. 23,    2003, pp. 479-493-   (15) Aliasing in human foveal vision, David R. Williams, Vision    Research, Vol. 25, No. 2, 1985, pp. 195-205-   (16) Learning to Perceive Features below the Foveal Photoreceptor    Spacing, M. Fahle, in Perceptual Learning, M. Fahle and T. Poggio,    2002 MIT Press, pp. 197-218-   (17) Sarver and Associates, Inc., www.sarverassociates.com-   (18) Austin Roorda, “The limits of high contrast photopic letter    acuity with adaptive optics,” 7th Wavefront Congress, (Jan. 26-29,    2006), http://www.wavefront-congress.org/info/listing.asp under    “Ethan Rossi” in Adaptive Optics Applications-   (19) I. Lipshitz, “Thirty-four challenges to meet before excimer    laser technology can achieve super vision,” J. Refract. Sur., Vol.    18 (November/December 2002) pp. 740-743-   (20) P. Binder, A. Dreher. Visual Acuity and Contrast Sensitivity in    Subjects Using Wavefront Customized Spectacles, 2003 Annual AAO    Meeting, Anaheim, Calif.;-   J. Jethmalani, J. Chomyn, G. Abdel-Sadek, J. Lemperle, L.    Sverdrup, V. Fedoriouk, P. Globerson, P. Binder, S. Lai, A. Dreher.    Wavefront Guided Spectacle Lenses for Emmetropes and Myopes. 2004    Annual ARVO Meeting, Fort Lauderdale, Fla.;-   J. Sherman, A. Dreher. Night time driving enhancement with iZon    lenses. To be submitted, 2006,    http://www.optometricmanagement.com/article.aspx?article=71560;-   P. Globerson, A. Dreher. Vision Improvement with Wavefront Guided    Spectacle Lenses. 2005 Annual AAO Meeting, San Diego, Calif.-   (21) M. Webster, M. Georgeson, S. Webster, “Neural adjustments to    image blur,” Nature Neuroscience, Vol. 5, No. 9 (2002) pp. 839-840-   (22) P. Artal, L. Chen, E. Fernandez, B. Singer, S. Manzanera, D.    Williams, “Adaptive optics for vision: The eye's adaptation to point    spread function,” J. Refract. Sur., Vol. 19,    (September/October 2003) pp. S585-S587-   (23) Nicholas Wade, “An Upright Man,” Perception, Vol. 29 (2000) pp.    253-257-   (24) Walter Besenmatter, “Recent Progress in Binocular Design,”    Optics & Photonics News, November 2000, pp. 30-33-   (25) www.birdwatching.com/optics-   (26) Daniel Vukobratovich, “Binocular performance and design,” in    Current Developments in Optical Engineering and Commercial Optics,    SPIE Vol. 1168, (1989) pp. 338-351-   (27) IBID, Vukobratovich 1989-   (28) L. P. Osipova, V. V. Potikhonova, “Effect of hand tremor on    observation efficiency in binoculars,” Sov. J. Opt. Technol., Vol.    58, No. 9 (1991) pp. 542-544-   (29) L. P. Osipova, V. V. Potikhonova, “Terrain resolution limit    during observations with hand-held binoculars,” Sov. J. Opt.    Technol., Vol. 58, No. 2 (1991) pp. 88-90-   (30) IBID L. P. Osipova, (1991), Vol. 58, No. 2 & No. 8-   (31) S. Bara, T Mancebo, E. Moreno-Barriuso, “Positioning tolerances    for phase plates compensating aberrations of the human eye,” Applied    Optics, Vol. 39, No. 19 (2000) pp. 3413-3420-   (32) Learning to Perceive Features below the Foveal Photoreceptor    Spacing, M. Fahle, in Perceptual Learning, M. Fahle and T. Poggio,    2002 MIT Press, pp. 197-218-   (33) Barry Winn, David Whitaker, David B. Elliot, Nicholas J.    Phillips, “Factors affecting light-adapted pupil size in normal    human subjects,” Invest. Ophthalmol. & Visual Sci, Vol 35, No. 3,    (1994), pp. 1132-37-   (34) www.wickedlasers.com-   (35) M. D. Harris, A. E. Lincoln, P. J. Amoroso, B. Stuck, D.    Sliney, “Laser Eye Injuries in Military Occupations,” Aviat Space    and Environ Med, Vol. 74, No. 9 (2003) pp. 947-952-   (36) W. N. Charman, N. Chateau, “The prospects for super-acuity:    limits to visual performance after correction of monochromatic    ocular aberration,” Ophthal. Physiol. Opt., Vol. 23, (2003) pp.    479-493-   (37) Larry N. Thibos, “Does chromatic aberration hinder or help?”    5th Wavefront Congress, Whistler B C, February 2004,    http://129.7.217.162/VOI/index.htm-   (38) James S. McLellan et al., “Imperfect optics may be the eye's    defense against chromatic blur,” Nature, Vol. 417, 9 May 2002, pp.    174-176-   (39) IBID, W. N. Charman 2003-   (40) J. Sheedy, R. F. Hardy, J. R. Hayes, “Progressive addition    lenses—measurements and ratings,” Optometry Vol. 77, No. 1 (2006)    pp. 23-29-   (41) For Instance see A. Guiaro, I. G. Fox, D. R. Williams, “Method    for optimizing the correction of the eye's higher-order aberrations    in the presence of decentrations,” J. Opt. Soc Am A, Vol. 19, No.    1 (2002) pp. 126-128; Ophthonix has a proprietary mathematical    method for generating high-order zones with large field-of-view.-   (42) Principles of Hartmann-Shack Aberrometry, Larry N. Thibos,    Wavefront Sensing Congress, Sante Fe, N. Mex., 2000,    http://research.opt.indiana.edu/Library/VSIA/VSIA-2000_SH_tutorial_v2/sld001.htm,    Introduction to Wavefront Sensors, Joseph M. Geary, SPIE Press 1995-   (43) The self-Imaging Phenomenon and its Applications, Krzysztof    Patorski, in Progress in Optics, Vol. XXVII, edited by E. Wolf,    North Holland 1989, pp. 1-108-   (44) Wavefront Sensor Using Near-Field Diffraction Effects, Larry    Horowitz, 5th International Congress on Wavefront Sensing and    Optimized Refractive Correction, Whistler, Canada, Feb. 21-23, 2004:    US Larry S. Horwitz, System and Method for Wavefront Measurement,    U.S. Pat. No. 6,781,681, Aug. 24, 2004-   (45) Wavefront Sciences COAS-HD instrument, Albuquerque, N. Mex.,    505-275-4747    http://www.wavefrontsciences.com/ophthalmic/COAS-HD.html-   (46) Larry N. Thibos, Xin Hong, Clinical Applications of the    Shack-Hartmann Aberrometer, Optometery and Vision Science, Vol. 76,    No. 12, December 1999-   (47) Eyeglass Manufacturing Method using Variable Index Layer,    Andreas Dreher, U.S. Pat. No. 6,712,466, Mar. 30, 2004-   (48) Achromatic hybrid refractive-diffractive lens with extended    depth of focus, Angel Flores, Michael R. Wang, Jame J Yang, Applied    Optics, Vol. 43, No. 30, 2004, pp. 5618-5630-   (49) Eyeglass Manufacturing Method using Variable Index Layer,    Andreas Dreher, U.S. Pat. No. 6,712,466, Mar. 30, 2004-   (50) Eyeglass Manufacturing Method Using Variable Index Layer,    Andreas W. Dreher, U.S. Pat. No. 6,712,466 (2004); U.S. Pat. No.    6,840,619 (2005); U.S. Pat. No. 6,942,339 (2005); Wavefront    Aberrator and Method of Manufacturing, Donald G. Bruns, U.S. Pat.    No. 6,813,082 (2004)

1. A method of manufacturing an optical element, the optical elementimproving contrast sensitivity, low-contrast visual acuity, and vernieracuity in one or more eyes of a subject, the method comprising:obtaining a prescription for the one or more eyes, wherein theprescription comprises corrections for one or more high orderaberrations in the subject's one or more eyes, wherein the prescriptionfurther comprises an aberration structure beyond a 3 mm diameter of thelens, wherein the aberration structure is selected to maximize amodulation transfer function (MTF) below a Nyquist resolution of thesubject's one or more eyes, wherein a Nyquist resolution limit of theNyquist resolution is a minimum visual acuity measured due to a conedensity in a human fovea; applying the prescription to the opticalelement, wherein the optical element is configured for use with nightvision goggles and further comprises a cured polymer, the cured polymermaterial comprising a fixed index of refraction, wherein the one or morehigh order aberrations are symmetrical high order aberrations, andwherein the method further comprises controlling limit aliasing in animage intensifier tube with a modulation transfer function.
 2. Themethod of claim 1, further comprising eliminating or modifying one ormore high order aberrations to produce an optimal visual acuity andcontrast sensitivity.
 3. The method of claim 1, wherein the opticalelement further comprises a three-layered structure, the method furthercomprising: correcting for the one or more low order aberrations of twoouter layers of the three-layered structure, wherein a center layer ofthe three-layered structure comprises a sandwiched cured polymermaterial that has a fixed index of refraction that corrects the one ormore high-order aberrations.
 4. The method of claim 1, furthercomprising correcting aberrations introduced during manufacturing beforeone or more high order aberrations of the subject's one or more eyes arecorrected.